Method of sidetracking wells



Sept. l2, 1939.

A. L. ARMENTROUT E T AL METHOD OF SIDETRACKING WELLS bia 4 J WM ff/'f/Q//a/wcg/ 2 Sheets-Sheet 1 Filed Feb. 16, 1958 Sept. l2, 1939. A. L. ARMENTROUT ET AL METHOD 0F SIDETRACKING WELLS 6, 2 Sheets-Sheet 2 Filed Feb. l

Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE METHOD 0F SIDETRACKING WELLS Application February 16, 1938, Serial No. 190,739

11 Claims.

This invention relates to well drilling and producing operations and relates more particularly to a method and apparatus useful in producing and sidetracking deep wells such as oil Wells and gas wells.'

When an oil well or gas well has been drilled and put in condition for production, it is sometimes found that the well does not produce in payingquantities or that it produces too large a proportion of Water or other unwanted fluid. In other instances a Well will become exhausted of its oil or gas after a short period of production. In such cases, and under various other circumstances, it is sometimes desirable to divert or sidetrack a well or deepen the well after it has been finished and equipped for production. Heretofore when such a course .was to be pursued it was necessary to pull the liner from the well or to attempt to cut through the wall of the set steel liner or the set steel casing. lMuch diillculty and delay is often encountered in the removal of a liner, particularly if the well has been producing for some time, and it is usually quite diicult to sidetrack through a set steel casing or liner.

An object of this invention is to provide a rapid and easily performed method for diverting or sidetracking a well that is equipped with a set casing or liner for production purposes, and that may or may not have been in production.

Another object of this invention is to provide a'simple method for sidetracking or diverting a well at a predetermined point or elevation through the set casing or liner and in any selected direction.

Another object of the invention is to provide a. method for sidetracking a well that does not necessitate cutting through' the set.water string or casing, nor the breaking of the cement seal about the same whereby a liner of the s ame size as originally employed may be installed in the diverted well and avoiding the necessity of landing and cementing a smaller casing.

Another object of this invention is `to provide a method for sidetracking a completed well in any selected direction that does not necessitate the employment of special milling tools, or the like, for cutting out through the casing or liner.

Another object of the invention is to provide a method for sidetracking a well'that assures the complete sealing oi of the strata bearing unwanted uid and penetrated by the lower portion of the well, as originally drilled.

Another object of this invention is to provide an apparatus for equipping a well for the produc- (Cl. Z55-1) tion of its fluid that facilitates the easy sidetracking of the well.

. Another object of the invention is to provide apparatus for equipping a well for production that provides for the subsequent sidetracking of the well at a predetermined point if and when such sidetracklng becomes necessary or desirable.

Another object of the invention is to provide a casing for lining a well that has a portion or section formed of drillable material whereby the well may be easily sidetracked from said section if and when it becomes desirable to sidetrack the well.

' A further object of the invention is to provide a liner for a producing Well that embodies a portion or section formed of drillable material whereby the wellv may be easily and quickly diverted or sidetracked from said section without removing theliner from the well and Without employing milling tools or the like to cut through a steel casing or liner.

Other objects and features of our invention will be better and more fully understood from the following detailed` description of typical forms a'nd applications of the apparatus and typical manners of carrying out the method, throughout which description reference may be had to the accompanying drawings, in which:

Fig. l is a longitudinal sectional view of the lower portion of atypical well showing one form of apparatus or liner arranged therein for production purposes. Fig. 2 is an enlarged fragmentary longitudinal sectional view of the well and liner illustrated in Fig. 1 showing the lower portion of the well occupied by cement. Fig. 3 is a view similar to Fig. 2.showing the upper portion of the liner and body of cement drilled out and a whipstock set in place to divert a drilling tool. Fig. 4 is a view similar to Fig. 1 illustrating another form of liner or casing arranged in the well. Fig. 5 is an enlarged fragmentary longl" tudinal sectional view illustrating the lower part of the casing of Fig. 4cemented in the well and a portion of the casing drilled away, and Fig. 6 is a view similar to Fig. 5 showing a whipstock in position to divert a drilling tool.

The method of the present invention may be carried out with the employment of apparatus constructed to suit diiferent conditions that may be encountered in deep wells such as oil wells and gas wells. In the drawings we have illustrated two typical forms of apparatus of the invention employed in the performance of the method. It is to be understood that the invention is not to be construed as restricted to the use of the typical preferred apparatus illustrated, or to the employment of the method under the particular circumstances about to be described. It is believed that the method will be better understood following a description of the typical preferred apparatus illustrated in the drawings and we will iirst proceed with a description of the apparatus.

In Figs. 1, 2 and 3 of the drawings we have illustrated the lower portion of a typical well W. The well W extends down through a number of spaced active or producing strata. In the simple case illustrated the well W penetrates a lower producing stratum A, a non-producing stratum B overlying the stratum A, a productive stratum C overlying the stratum B, and a non-producing stratum D overlying the stratum C. A casing I extends down in the well W from the ground surface and has its lower portion embedded or set in a body of cement I I in the portion of the well penetrating the non-producing stratum D. The open lower portion of the well W, continuing beyond the casing I0, may vary to a great extent in length, for example, it may be only one hundred feet in length or it may be several thousand feet in length.

'Ihe form of apparatus of the invention illustrated in Figs. l, 2 and 3 of the drawings is in the nature of a casing or liner L for the open lower portion of the well W and the liner L comprises, generally, an elongate tubular body having a drillable portion or section I2 and having one or more perforated portions as will be herein after described.

The liner L is adapted to be set or arranged in the well W to extend through its open lower portion. 'I'he liner L is provided to admit the iiuids produced by the producing sands or strata A and C and to conduct the same upwardly to the casing I IJ. The liner L serves to screen out or prevent the entrance of sand or other solid matter and to prevent caving or collapsing of the open lower portion of the well W. In most applications or installations the body or liner L is made up of a number of pieces or sections connected to form an elongate tubular structure. In the typical case illustrated the liner L comprises a perforate section I3 in the portion of the well W penetrating the producing stratum A, an imperforate section I4 in the part of the well penetrating the stratum B and the above mentioned drillable section I2 extending through the part of the well penetrating the stratum C.

Where the drillable section I2 extends through the part of the well W penetrating the producing stratum C, it is perforate to admit fluid of the said stratum.' While we have shown the perforate section I3 as being the lowermost section of the liner L it is to be understood that the liner may extend downwardly beyond the section I3 and Amay include other lower sections. 'I'he perforate sections I2 and I3 preferably extend completely through, or through substantial portions of their respective strata C and A; The perforate sectionsIZ and I3 may be provided with screen openings of various natures for the admission of the produced fluids. In the particular structure illustrated the sections I2 and I3 are provided with multiplicities of circumferentially and longitudinally spaced slots I 6 for admitting fluid from the well W to the interior of the liner L. The imperforate section I4 extends between and connects the two perforate sections I2 and I3 and in practice may be of any length that provides for the correct spacing of the sections I2 and I3 so that they are located in the producing strata C and A. Accordingly, the imperforate section I4 may be made up of any required number of connected lengths of tubular pieces or members.

In the drawings we have shown the sections I3 and I4 connected by a threaded collar or coupling I1 and the sections I2 and I4 connected by a similar collar or coupling IB. The liner L may be set, hung or retained in the well W in any selected manner. In the typical installation illustrated the liner L is supported on the lower wall of the well W, the lower section I3 being provided with a shoe I9 for engaging the bottom of the well. In accordance with the'invention the sections I3 and I4, the couplings I'I and I8, and the shoe I9 may be formed of steel in the usual manner.

'I'he drillable section I2 is a feature of the invention. The section I2 is such that it may be easily and quickly drilled away or drilled up when it becomes necessary or desirable to sidetrack the well. The removable or drillable section I2 is formed of a material that may be easily broken up or drilled up by a suitable drilling tool operated in the well. It is preferred to form the section I2 of aluminum or an aluminum alloy which can be readily drilled up by a suitable tool when in the well. The invention contemplates the formation of the section I2 of other drillable materials such as cement, glass, Bakelite, hard rubber composition, and the like, that possess the desired qualities. A desirable characteristic of the aluminum or aluminum alloy of which the section I2 may be formed is its low specic gravity whereby the fragments or cuttings of the section I2 formed when the section is drilled away readily ush or wash from the well W with the circulation fluid discharged from the drilling tool.

It is preferred that the liner L extend upwardly into the lower portion of the set well casing I0. In most installations it is preferred to locate the drillable section I2 in the liner L so that it occurs at or adjacent the lower end of the set casing I0. yIt is preferred to provide a head or outwardly projecting flange 2U on the upper end of the section I2. It will be observed that the several sections or parts of the liner L, with the exception of the section I2, may be formed of steel in the usual manner.

In carrying out the method of the invention with the apparatus illustrated in Figs. 1, 2 and 3, it will be assumed that the well W has been completed as illustrated and described above. Upon completion of the well the liner L is made up or assembled. The liner L is constructed so that its perforate section I3 will extend through the stratum A, its imperforate section I4 will extend through the stratum B and its perforate drillable section I2 will extend through the stratum C and project into the casing I0. The liner L may be run into the well W in the usual manner to the selected position. As described above, the liner L may be allowed to rest on the bottom wall of the well W when in its final position.

Following the setting or positioning of the liner L the well W is` allowed to produce from the strata A and C and the other producing strata, if any. In some instances it may be desirable or necessary to pump the well in the manner well known to those skilled in the art. It may be assumed that the well W is allowed to produce until its oil sands or producing strata become exhausted of the wanted uid, produce in insuflicient quantities, or ood the well with water, or it -may be assumed that upon completion of the well or immediately thereafter the well fails to produce in paying quantities. Under such circumstances it may beY desired to divert or sidetrack the well W in an attempt to penetrate an oil bearing sand out of alignment with the well, or to reach a lower oil sand. The method of the invention materially facilitates such a sidetracking operation.

In carrying out the sidetracking operation a body of cement slurry Sis introduced to the weil W. The cement S may occupy the well W from its lower end to a plane at or above the lower end of the set casing I0, as shown in Fig. 2. This, of course, imbeds or encases the liner L in a body or plug of cement slurry S. It is to be understood that it is not essential to encase the entire liner I.. in the cement S. The plastic cement or cement Subsequent to the hardening of the cement slurry S, a suitable well drilling tool such as a rotary drilling 'bit of the drag type.` or a rotary rock bit, is run into the well W and isoperated to drill out the upper portion of the body of cement S and the encased drillable liner section`i2. The section I2 being completely encased inthe cement S and being formed of a drillable material is readily drilled up into small fragments or cuttings by a suitable well drilling tool. The cuttings of the section I2 and the cuttings of the cement S are flushed from the well W with the circulation uid discharged under pressure from the drilling tool. The drilling operation is started at or above the upper end of the drillable section I2 and continues to a selected point some distance below the lower end of the set casing II). In practice the drilling operation may continue until the drilling tool engages the coupling I8 at which time the exposed major portion of the section I2 has been completely drilled away. The engagement of the drilling tool with the steel coupling I8 is accompanied by marked resistance to the cutting action of the drilling tool and this indicates to the operator that the section I2 has been completely drilled away.

Fig. 3 ofthe drawings illustrates the condition of the well W following the drilling away of the section I2 and the upper portion of the body of cement S. The drilling away of the section I2 and the upper portion of the body of cement S provides or leaves an upwardly facing shoulder'or surface 2I -at the upper end of the` collar or coupling I8'. Where the drillable section I2 is of substantial length, the drilling operation just described provides or leaves a portion of the well W of substantial length that is clear and open. It will be observed that the cementing in of the liner L preceding the drilling operation completely seals off the stratum A and any other producing strata below the coupling I8 to prevent unwanted fluid in such strata from entering the well W.

Following the drilling up of the section I2 and the drilling away of the upper portion of the body of cement S, a whipstock 22 is run into the well W to occupy a position in the open portion ofthe well. The whipstock 22 may be arranged on the surface 2l to be supported thereby and to occupy a desired or selected position in the open portion of the well W at the stratum C or D. In accordance with the invention any suitable type of whipstock may be utilized. The

whipstock 22 illustrated has an inclined surface l 23 for diverting the drilling tools and has a ring or sleeve 24 at its upper end adapted to t about the drill stem or operating string 25 of asidetracking bit 26. The particular whipstock 22 illustrated may be run into the well W on the string 25 with its sleeve 24 releasably connected with the bit 26. This facilitates-the orienting of the whipstock 22 by means of the drilling string 25. The above described drilling away of the section i2 and the upper portion of the body of cement S leaves a part of the well W free and unobstructed so that the whipstock 22 may be easily oriented and set as desired.

When the 4whipstock 22 has been arranged in the selected position the drilling string 25 is rotated and fed downwardly so that the engagement of the bit 26 with the surface 23 results in sidetracking of the bit. As illustrated in Fig. 3 of the drawings'the bit 26 drills into the side wall of the well W to form a hole or bore 28 that is inclined with respect tothe well W.l When the bit 26 leaves the whipstock 22 it may continue in the path indicated. It is to be particularly noted that the sidetracking blt 26 acts directly upon the earth formation at the side wall of the lwell W and does not engage or penetrate any part of the casing Il) or the liner L. This clearly facilitates the sidetracking operation and assures a successi'ulsidetracking of the well W. When the bit 26 hasmade a bore 28 of the desired length the string 2 5 may be withdrawn from the well to remove the"bit-and the whipstock 22. obvious how fire well' bore or sidetrack bore 28 may be continuedor deepened with suitable drilling tools to the 'desired depth.

Figs. 4, 5 and 6 illustrate another form of apparatus of the invention arranged in a well W having an open lower portion penetrating an'oii sand or productive stratum A', an unproductive stratum B', a productive stratum C' and a nonproductive stratum D. A casing I Ila is set in the well W' and has its lower portion cemented in the stratum D. 'I'he apparatus of the invention shown in Figs. 4, 5 and 61s in the nature of a cas- Aing 33 having an upper portion 3I extending down through the casing III, a drillable section 32 in the open portion of the well W' and perforate sections 33 and 34.

'I'he casing 33 is provided to line or case the open lower portion of the well W' and to conduct the produced fluid to the ground surface. The casing is an elongate tubular structure or assembly extending through the well W and to or through the lower producing stratum A. The upper portion 3| of the casing 30 may be made up of a large number of lengths of casing and is of suflicient length to extend from the upper end of the well toI a point adjacent or below the lower end of the casing I 0. The major upper portion 3l ofA the casing C may be constructed of steel in the usual manner. The lower end -part of the portion3l preferably extends into the open portion of the well W'. and is preferably provided with a cement basket 35. Cement 36 is introducedinto the well W above the basket 35 to cement or set the casing 3|! in the well. In actual practice the portion 3| may extend aconsiderable distance beyond the lower end of the casing |011- and the cement 36 may encase or surround the portion 3I for a substantial distance.

The drillable casing section 32 is preferably,

VIt win be I though `not necessarily connected with the lower end of the portion 3l. A suitable threaded collar or coupling 31 may connect the upper end of the section 32 with the lower end of the portion 3|. In the case illustrated where the section 32 extends through the non-productive stratum D', the section 32 is imperforate. In accordance with the invention the section 32'is drillable, that is, it is formed of a material that may be drilled up or reduced to small fragments or cuttings by a suitable well drilling tool when 4the casing 39 is in the well W. It is preferred to construct the section 32 of aluminum or a suitable aluminum alloy which can be readily drilled up. It is to be understood that the section 32 may be formed of other drillable materials such as glass, cement, Bakelite, hard rubber composition, etc. In the drawings we have shown the lower end of the drillable section 32 connected with the perforate section 33 by a collar or coupling 33. It is to be understood, however, that one or more imperforate sections or lengths of casing may be interposed between the lower end of the drillable section 32 and the perforate section 33. The couplings 31 and 33 are preferably formed of steel or the like.

The perforate casing sections 33 and 34 are lengths or assemblies of tubular casing stock perforated or provided with spaced slots 39. An imperforate casing section 4U is interposed between the perforate sections 33 and 34 to extend through the non-productive stratum B. Suitable couplings 4I may connect the perforate sections 33 and 34 with the imperforate section 4i). A shoe 42 may be provided on the lower end of the lower perforate section 34. The sections 33, 34 and 40, the couplings 38 and 4l and the shoe 42 may be formed of steel. The casing 3U may be suspended from the top of the well by a casing head or the like i not shown), so that the shoe 42 hangs free of the bottom of the well W. It will be observed that the casing 3|) with the exception of its section 32 may be formed of steel in the usual manner.

In carrying out the method of the invention with theapparatus illustrated in Figs. 4, 5, and 6, it will be assumed that the well W has been drilled to the depth shown in Fig. 4 and that the casing Il)a has been set or cemented in place. The casing 30 is made up and run into the well in the usual manner. The casing 30 is assembled so that its several parts and sections will be in the positions illustrated in Fig. 4 of the drawings when the casing is set or hung in the well. Following the running ofNthe casing 30 to'the proper position in the well, the cement 36 is introduced into the well W to encase the section 3l for some distance above the basket 35. This cement 33 may be introduced in any of the well known manners and when set and hardened serves to hold or cement the casing in the well and to seal olf the producing open lower portion of the well W' from the remainder of the well.

When the casing 30 has been set as described above, the well may be allowed to produce from its strata A and C and if necessary, may be pumped. The produced or pumped fluid enters through the perforations or slots 39 in the sections 33 and 34 and passes up through the casing 35. After a prolonged period of production, the well may become depleted of its oil and gas or may become sanded up. For the foregoing or other reasons, it may be desired to redrill or deepen the well by diverting it from the original hole. In accordance with the invention, the rst step in pursuing this course is to introduce a body of cement 44 into the well W' to encase or cement in the casing sections 32, 33, 34 and 40. The cement 44 may be introduced through the casing 30 in a plastic state or in the form of a slurry and forced out through the slots 39 to occupy the annular space in the well W surrounding the casing. The cement 44 may also occupy the interior of the casing 30 to a point adjacent or below the lower end of its portion 3l. It is preferred to introduce sucient cement 44 to substantially completely encase and occupy the drillable section 32 as well as the lower portions of the casing 30. The cement 44 is allowed to set and harden to rigidly secure the lower parts of the casing 30 in the well W.

Following the hardening of the cement 44 the section 32 or a part of the section 32 is drilled out. In performing this operation a suitable well bit, under-reaming tool, wall scraper or the like, is run down through the casing 30 on an operating string and is operated to drill up the section 32. This drilling up of the section 32 is accompanied by the drilling away of the cement 44 occupying the interior of the section 32 and a portion or all of the cement enclosing or surrounding the section 32. As the -section 32 is set or imbedded in the cement 44, it is readily drilled up or reduced to small cuttings or fragments by the drilling tool or reaming tool. The circulation fluid discharging under pressure from the drilling or underreaming tool flushes away the cuttings or fragments of the section 32 and the cuttings of the cement 44 and carries the same to the ground surface.

In practice it may be preferred to drill away a substantial portion of the section 32. Fig. of the drawings illustrates the condition of the equipment following the drilling or underreaming operation just described. As illustrated in Fig. 5 of the drawings, a substantial part of the section 32 has been cut away to leave an enlarged opening 45 in the body of cement 44. The opening 45 may be of such diameter that a thin wall of cement 44 remains to surround it. It is to be understood, however, that the tool employed to drill up the section 32 may be capable of drilling away all of the cement 44 around the section 32 to expose the earth formation at the side wall of the weil W. When a sufficient part of the section 32 has been drilled up the drilling tool is withdrawn from the well W.

The next phase or step of the method is the arrangement of a suitable whipstock 46 in the opening 45. The whipstock 46 may be of any suitable type and may be set and oriented in any known manner. in the drawings is of the same type as the whipstock 22 and is adapted to be run into the well through the casing 30 on a sidetracking bit 26a. The sidetracking bit 2lia is secured to the lower end of an operating string 41 and the whipstock 45 has a collar or sleeve 48 that is releasably connected with the bit when the same is run through the casing. This association of the whipstock 46 with the bit 26a and the string 41 facilitates the orienting of the whipstock by means of the string. The whipstock 46 is adapted to be arranged in the opening 45 so that its lower end engages the bottom wall 4.9 of the said opening. This bottom wall 49 is provided by the body of cement 44 and constitutes a firm dependable footing for the whipstock.

When the whipstock 46 has been oriented and set in the opening 45, the string 41 is manipu- The whipstock 46 illustrated lated and operated so that the bit 26 is deflected by the surface 50 of the whipstock to drill a diverging bore 5I in the earth formation. The whipstock 46 may rest against the side wall of the opening 45 and the bottom wall 49 of the opening and is dependably supported for the whipstocking operation. It is to be particularly noted that the bit 2liEl diverted by the whipstock 46 may readily drill out through the Athin wall of cement 4I and then pass directly into the earth formation without contacting a steel casing 4or a steel liner; The bit 26, of course, may be operated to drill to any desired depth and the bore 5|! may be continued and directed as desired.

Having described only typical preferred forms and applications of the method and apparatus of our invention, we do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to ourselves any modifications or variations that may appear to those skilled in the art or fall within the scope of the following claims.

Having described our invention, we claim:

l. The method of operating a well which comprises arranging in the well a tubular body having at least one perforate portion for receiving the fluid from the earth formation and having a drillable portion, allowing said fluid to enter through said body, and subsequently when occasion requires sidetracking through said drillable portion.

2. The method of operating a well which comprises providing a .tubular body having a drillable portion and having at least one perforate portion for admitting fluid, arranging the body in the well so that the uid from the earth formation may enter through said periorate portion, drilling up said drillable portion to leave a portion of the well clear, and then sidetracking the well from said clear portion.

3. The herein described method which comprises providing a tubular body having at least one perforate portion and a portion formed of drillable material, arranging the body in the lopen productive portion of a well so that the perforate portion may receive the formation iiuid, and subsequently when occasion requires operating a tool in the well to drill up said drillable portion of the body to leave a part of the well clear and then sidetracking the well through said clear part.

4. The herein described method which comprises providing a tubular body having at least one perforate portion and a portion formed of drillable material, cementing the body in the open productive portion of a well so that the perforate portion may receive the formation fluid, subsequently when occasion requires drilling up `said drillable portion, and then sidetracking the well from the area of drilling up said drillable portion,

of the body. l

5. The herein described method which comprises provlding-.a tubular body having at least one perforateV portion and a portion formed of ydrillable material, arranging the body in the open productive portion of a well so that the yperforate portion may'receive the formation uid, cementing the said body in the well, subsequently when I occasion requires operating a tool in the well to \drill up ksaid drillable portion ofthe body to leave a part of the well clear, and then sidetracking the well byv arranging a whipstock in said clear part of the well, and directing a drilling bit from the well by means of the whipstock.

6. The herein described method which comprises providing a tubular body having at least one perforate portion and a portion formed -o'f drillable material, arranging the body in the open productive portion of a well so that the perfor-ate portion may receive the formation fluid, subsequently when occasion requires `operating a tool in the well to drill up said drillable portion of the body to leave a part of the well clear, arranging a whipstock-in said clear part of the well, and then deflecting the well by operating a drilling tool against the whipstock to divert the drilling tool into the formation from said clear part of the well.

'7. The herein described method useful in the operation of a. well having an open producing lower portion which-comprises providing a liner having a perforate portion and a drillable portion, arranging the liner in the open portion of the well to permit production vof the well fluids through the liner, subsequently when occasion requires cementing the liner in the well, operating a tool in the well to drill up said drillable portion and part of the cementV to provide an open space in the well, arranging a whipstock in said open space, and diverting a drilling tool by means of the wihpstock to divert the well.

8. 'I'he herein described method useful in the production of a well having an open producing lower portion which comprises arranging a casing in the well having a drillable portion and a 4perforate portion in said producing portion of the 9. The hereindescribed method useful in the production of a well having an open producing lower portion which comprises arranging a casing in the well having a drillable portion and a perforate portion in said producing portion of Ythe well, producing the well uidsthrough the casing, subsequently when occasion requires cementing up said producing portion of the well,

' operating a tool in the well to drill up said drillable portion and thus leave an open space in the well, arranging a whipstock in the,v said open space, and then directing a drilling tool by means ofthe whipstock to divert the well.

10. The method of operating a well which comprises arranging in the well a tubular body having at least one portion for lreceiving the fluid from the earth formation and having a drillable portion, allowing said fluid to enter through said tubular body, and subsequently when occasion requires sidetracking the well through said drillable portion.

11. The method of operating a well which includes arranging in a well a tubular body having one ormore connected lower steel sections and one or more readily drillable sections thereabov'e, and subsequently when occasion Irequires closing at least the top of the lower steel sections and deilecting the well through the locality 'of the drillable sections.

ARTHUR L. ARMENTROUT. l I ELWIN AB. HALL. 

